Pre-Atoka Rocks of Northern Arkansas GEOLOGICAL SURVEY PROFESSIONAL PAPER 314-H Pre-Atoka Rocks of Northern Arkansas By SHERWOOD E. FREZON and ERNEST E. CLICK SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 314-H Thickness, lithofacies, and geologic history of potential oil and gas producing rocks of Paleozoic age in northern Arkansas UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1959 UNITED STATES DEPARTMENT OF THE INTERIOR FRED A. SEATON, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director The U. S. Geological Survey Library has cataloged this publication as follows: Frezon, Sherwood Earl, 1921- Pre-Atoka rocks of northern Arkansas, by Sherwood E. Frezon and Ernest E. Glick. Washington, U. S. Govt. Print. Off., 1959. iii, 171-189 p. maps, diagrs., table. 30 cm. (U. S. Geological Sur­ vey. Professional paper 314-H. Shorter contributions to general geology) Part of illustrative matter fold, col., in pocket. Bibliography: p. 186-187. 1. Geology Arkansas. 2. Rocks, Sedimentary. 3. Geology, Strati- graphic Paleozoic. i. Glick, Ernest Earwood, 1922- joint author, n. Title. (Series: U. S. Geological Survey. Professional paper 314-H. Series: U. S. Geological Survey. Shorter contribu­ tions to general geology) 551.7209767 For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. CONTENTS Page Abstract .__----_ ---_-_._--._---__-_-____ 171 Stratigraphy Continued Page Introduction. ___ ___________________________________ 171 Probable latest Mississippian and early Pennsyl- Structural features____________^___._________________ 172 vanian rocks..____-_--_--___--_---_--_---_-_- 180 Stratigraphy _-_--__-_--____--__-_-__-____-______-__ 173 Bocks of the interval between the Pitkin lime­ Precambrian rocks._____________________________ 173 stone and the Prairie Grove member of the Cambrian rocks-_--_---___-_-___-----______-__- 176 Hale formation (or its apparent equivalent to Ordovician rocks.______________________________ 176 the south and east of Washington County).- 181 Pre-Everton rocks-___-_--___-____-__--_____ 176 Prairie Grove member of the Hale formation in Everton formation and St. Peter sandstone. _ _ 176 Washington County and its apparent equiv­ Post-St. Peter rocks_______________.___ 177 alent to the south and east.________________ 182 Silurian rocks._________________________________ 177 Bloyd shale in Washington County and its Devonian rocks_______________________________ 177 apparent equivalent to the south and east __ 183 Penters chert_______________________ 177 Depositional history______-.___-___-______-____-__-- 183 Clifty limestone___-_-__--_-______________ 178 Oil and gas_-____--__-_-_-------_----__----_-_--__- 185 Rocks of Mississippian and Devonian age__-__-____ 178 Literature cited_________.__-___-________--__-___. 186 Chattanooga shale__________________________ 178 Index.__________________________________________ 189 Mississippian rocks _____________________________ 179 Boone formation__________________________ 179 Moorefield formation to Pitkin limestone._____ 180 ILLUSTRATIONS [Plates are In pocket] PLATE 20. Structure of the Boone formation and location gas fields producing from rocks of Morrow age. 21. Thickness of the Everton formation and the St. Peter sandstone combined, and percentage distribution of sandstone. 22. Thickness of post-St. Peter rocks of Ordovician age. 23. Thickness of rocks of Silurian age. 24. Areal distribution of pre-Chattanooga rocks, and thickness of the Penters chert. 25. Thickness of the Chattanooga shale exclusive of the basal sandstone member. 26. Thickness of rocks of Mississippian age (Boone to Pitkin) and percentage distribution of limestone. 27. Thickness of the Boone formation and percentage distribution of shale. 28. Thickness of Moorefield-to-Pitkin sequence, and percentage distribution of limestone. 29. Thickness of rocks occupying the interval between the Pitkin limestone (or Fayetteville shale) and the Prairie Grove member of the Hale formation (or its apparent equivalent south and east of Washington County), and percentage distribution of sandstone. 30. Thickness of the Prairie Grove member of the Hale formation in Washington County and of its apparent equivalent south and east of that area, and percentage distribution of limestone. 31. Thickness of the Bloyd shale in Washington County and of its apparent equivalent to the south and east of that area, and percentage distribution of limestone. Page FIGURE 37. Index map of Arkansas showing geographic regions and area of accompanying maps. _____________ 172 TABLE Pre-Atoka formations of northern Arkansas--__-___-_-_____--_.________-___-____. ___-___------_-------------------- 174 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY PRE-ATOKA ROCKS OF NORTHERN ARKANSAS By SHERWOOD E. FREZON and ERNEST E. ABSTRACT thickness of the chert and limestone beds of the Boone forma­ The part of Arkansas discussed in this report lies north of tion (Mississippian) decreases to the west and south from the the Ouachita Mountains and west of the Gulf Coastal Plain type area in north-central Arkansas, and southeastward the and includes parts of the Ozark region and the Arkansas formation grades into black shale. The thickness distribu­ Valley. Pre-Atoka rocks of Ordovician, Silurian, Devonian, tion of Moorefleld-to-Pitkin rocks (Mississippian) is similar Mississippian, and early Pennsylvanian age crop out in the to that of the total thickness of Mississippian rocks. Ozark region, dip southward under a cover of thick Atoka and The thickness of rocks of Morrow age increases to the south younger Pennsylvanian rocks in the Arkansas Valley, and re­ and southeast. The percentage of sandstone in the interval appear at the surface in the Ouachita Mountain region. Out­ between the Pitkin limestone (or the Fayetteville shale) and crops and wells provide data on the pre-Atoka rocks in the the Prairie Grove member of the Hale formation (or its appar­ Ozark region and the northern part of the Arkansas Valley; ent equivalent south and east of Washington County) increases few wells have been drilled in the southern part of the Arkan­ to the northeast and northwest from the south-central part of sas Valley and correlations of pre-Atoka rocks between the the area. The percentage of limestone in the Prairie Grove northern part of the Arkansas Valley and the Ouachita Moun­ member of the Hale formation and the Bloyd shale of Wash­ tain region cannot be made directly. ington County and of their apparent equivalents south and east The regional structure of pre-Atoka rocks of the Ozark region of that area decreases to the east and southeast. and the northern part of the Arkansas Valley is reflected by the The pre-Atoka Paleozoic rocks of northern Arkansas are regional structure of the base of the Boone formation. The dominately marine. Pre-Chattanooga rocks, which are domi- regional dip of the base of the Boone formation increases grad­ nately marine carbonate sediments, were deposited, in relatively ually from 10 feet per mile to 200 feet per mile southward shallow, extensive seas. Until the end of St. Peter time, sand across the Ozark region, and steepens to as much as 500 feet was swept intermittently into the area and deposited, but after per mile along the northern limb of the Arkansas Valley St. Peter time, Ordovician, Silurian, and Devonian sediments geosyncline. were deposited in seas relatively isolated from sources of coarse Thirty-two pre-Atoka formations, ranging from Cambrian to clastic sediments. Numerous periods of uplift and erosion early Pennsylvanian in age, crop out in northern Arkansas interrupted deposition in pre-Chattanooga time and the dis­ and southern Missouri but subsurface data are sufficient to tribution of the pre-Chattanooga rocks indicates that consider­ determine the regional thickness and lithofacies of only the able areal truncation preceded the deposition of both the Bverton formation (Ordovician) and younger rocks. The Penters chert and the Chattanooga shale. Mississippian sand­ Bverton formation and St. Peter sandstone (Ordovician) com­ stones, shales, limestones and cherts were deposited on a shelf bined, a predominantly dolomite and sandstone unit, increases area in northern and western Arkansas and in a deeper basin to in thickness to the south and east and contains a greater per­ the south and east of the shelf. The dominately clastic pre- centage of sandstone to the northwest and northeast. The Atoka sediments of Pennsylvanian age were deposited in shallow series of limestone beds and the overlying shale, which makes seas. The area was uplifted and eroded before the deposition up the post-St. Peter rocks of Ordovician age, increases in of the Atoka formation. thickness to the southeast but the individual formations of the No commercial quantities of oil have been found in northern unit do not change in lithology in the area. Silurian rocks Arkansas, but commercial quantities of gas have been produced and the Penters chert (Devonian) increase in thickness to the from 5 zones in the pre-Atoka rocks of the area, as well as south in the western two-thirds of the area and decrease in from several zones in Atoka rocks. It is probable that addi­ thickness to a truncated edge in the southeastern part of the tional gas will be discovered in pre-Atoka rocks in northern area. The Chattanooga shale increases in thickness south­ Arkansas. Source beds, reservoir rocks, and geological struc­ ward into the Arkansas Valley and westward in Benton, Wash­ tures present